mathewson



3 SheetsSheet 1.

(No Model.)

J. E. MATHEWSON. SAND BLAST APPARATUS. No. 409,751. Patented Aug. 27, 188-9.

(No Model.)

J. E. MATHEWSON. SAND BLAST APPARATUS.

3 Sheets-Sheet 2.

Patented Aug. 27, 1889.

(No Model.)

3 Sheets-Sheet; 3 J. E. MATHEWSON.

SAND BLAST APPARATUS.

No. 409,751. Patented Aug. 27, 188 9.

UNITED STATES PATENT OFFICE.

JEREMIAH E. MATHEWVSON, OF SHEFFIELD, COUNTY OF YORK, ENGLAND.

SAN D-BLAST APPARATUS.

SPECIFICATION forming part of Letters Patent No. 409,751, dated August 27, 1889. Application filed August 30, 1388. Serial No. 284,196. (No model.)

cess of sharpening files and cutting stone,

glass, metals, and other substances by the sand-blast. This is due not only to the necessity for frequently renewing the nozzles, but also to the fact that the cutting action, which is at its maximum of efficiency at or soon after the starting of the blast, becomes less and less efficient as the operation proceeds.

Now the object of the present invention is to remove these serious disadvantages and thereby to effect an important economy both in the cost of maintenance of the apparatus and in the power and time required to produce a certain quantity of work.

It is well known that the abrasion of the nozzles is due to the sand or other cutting material receivingits impulse while contained Within the nozzle. Byaseries of experiments I have discovered that if the streams of propelling-fluid and sand or cutting material are kept apart until they leave the blast-pipe, and

,if the steam or air on leaving the mouthpiece is caused to converge either to a central point or tea line in front of the mouth-piece and there strike the issuing stream of sand a perfect mingling of the sand with the steam or air will take place and no cutting action will occur until the sand-blast meets the work.

I may use in carrying out my invention either a circular mouth-piece or a broad flat mouth-piece, or forms intermediate of these, according to the work in hand, with the like beneficial result. I will first describe the invention as applied to a fiat mouthpiece and afterward to a round mouth-piece.

In the accompanying drawings, Figure 1 shows in plan view, Fig. 2 in longitudinal section, and Fig. 3 in front or end View, a mouth-piece such as I employin finishing and sharpening files and rasps and working over broad surfaces; Figs. 4: and 5 show in longitudinal section and end view a circular mouthpiece suitable for general work such as cutting, frosting, and ornamenting glass and metallic surfaces or boring holes in glass and other materials, and Fig. 6 is a diagram which illustrates the action of the invention.

Before describing the construction of the mouth-pieces I will, by reference to the dia gram, Fig. 6, explain the manner in which the cutting material and the steam or air blast are mingled at and beyond a point clear of the mouth-piece. In this diagram, 1 is the passage for the cuttingmaterial, and 2 2 are passages (on opposite sides of the passage 1) for the steam or air under pressure to pass out and converge in a plane (indicated by the line 3 3) in advance of the passage 1. The streams of steam or air in thus converging will form a slight vacuum in front of the passage 1, facilitate the feed of the cutting material and cause it to mingle with the in1pelli'ngfluid,as indicated by the dots in the diagram. Thus the mingling, instead of takingplace,as heretofore, within the nozzle or mouth-piece and in contact with the metal, will occur in front of the mouth-piece, and thereby the abrading action, so detrimental to the efficiency of the apparatus, will be avoided.

In Figs. 1 and 2, A is a casting forming the main portion of the mouth-piece, and

B B are plates bolted to opposite sides of the mouth-piece. In this casting A there is cored out a steam-passage a, which diverges from a cylindrical to a forked shape at a. This forking of the steam-passage is produced by a transverse wall of metal, which constitutes the back of a chamber 0, that opens in the form of a slit 0 at the front of the mouth-piece. Access is obtained to this chamber by side openings in the casting A, for the purpose of inserting therein a sand-tube D, connected with a reservoir for the sand or other cutting material. This tube D is preferably tapered toward its closed end, and at its back is formed a rib which enters a transverse slot cut in the back of the chamber to insure its proper insertion in the m outh-piece.

The front of this tube D has a longitudinal opening covered by a flattened tube or parallel lips cl, closed at their ends. Thus a passage is formed for conducting the sand from the tube D to the slit or exit-opening c in the chamber 0. By this mode of fitting the tube in place as little metallic cont-act as possible is established between the chamber and the tube. The object of this arrangement is to prevent the heat of the impelling-fluid from so acting upon the cutting material (when wet sand or mud is used) as to choke the action of the apparatus.

The plates B B fit close upon slightly-raised ribs at the sides of the casting A, and form at their back and sides steam-tight joints with the casting. These plates converge slightly toward the front of the mouth-piece, and serve to form extension-passages b b, from which the impelling-fiuid issues in thin streams, converging at an angle of some fifteen degrees toward the plane of progress of the stream of sand or cutting material,where they meet the same and mingle therewith, as above explained with reference to Fig. 6. The chamber C terminates in a straight mouth 0, parallel with the exit-openings of the stean1-passages b b. The mouth of the passage 0 is flush with the exit ends of the passages b b, but its width is somewhat less than the width of those passages.

For the purpose of delivering the sand or cutting material freely from the mouth-piece, I employ pressure (by gravitation or otherwise) to insure the steady feed of the material through the apparatus; and to provide against injury to the mouth cof the chamber 0, any bruising or notching of which would detract from the evenness of the stream,I form the plates 13 with lips, which overhang the openings for the issue of the steam without interfering with its travel. This provision, it will be understood, is simply a guard for maintaining the efficiency of the apparatus against rough usage.

E E are detachable plates set at opposite ends of the outlet-passages b b, to prevent air entering between the streams of steam and interfering with the steady flow of the cutting material. These plates, which are made preferably of steel, are held in place against the plates B by binding-screws, which pass through screwed lugs formed on the casting A.

F is aloop cast in one with the mouth-piece A, and intended to receive a feeler G, which beds upon a raised portion of the upper plate 13, and serves as a support and testing-piece for the file or rasp presented to the action of the sand-blast.

In the circular portion of the passage a a screw is cut to allow of the mouth-piece being secured to the steam-supply pipe. \Vhen steam is delivered to the mouth-piece, and sand or other cutting material is admitted to the pipe D, a jet of mingled steam and sand will be formed beyond the mouth-piece, of a shape roughly corresponding, when striking the work, to the exit end of the mouth-piece.

For general work I use a circular mouthpiece, the size of which will depend upon the work it is required to perform. Thus when a jet corresponding more or less with a pencil point is required I propose to employa circular mouth-piece with an air-exit of about onethird the diameter of that shown at Figs. 4 and 5, or, say, one-eightl1 of an inch outside diameter. In this case an annular jet is formed, which surrounds the extruded feed of cutting material and strikes it at a point beyond the mouth-piece, mingling with the cutting material and producing an incisive jet, the diameter of which will increase according to the distance from the point of concentration at which the jet strikes the work.

In Figs. 4 and 5, II is a straight tube in communication with a reservoir of dry sand or other cutting material, which is supplied by gravitation to the tube II. This tube fits into the centerof a tubular castingI, which terminates on a level with the exit end of the tube H, and is supplied with steam or air under pressure through a branch I in communication with a steam-boiler, or air-pump, or reservoir, as the case may be. The steam or air entering the tubular casting I surrounds the tube H and passes out in the form of a hollow tapering jet, drawing with it a stream of sand or cutting material which meets the steam or air at a point in advance of the mouth-piece, as in the first-described arrangement. Here the sand and the steam or air unite, and mingling, as illustrated in the diagram, Fig. 6, form a cutting-blast, which, when presented to a metallic or other surface will abra'de it, either evenly in the form of lines or hard or softened shadows, the distance between the point of concentration of the steam or air and sand and the surface of the plate under treatment being varied to produce these varying results, according to the nature of the work in hand.

I may remark that by slightly retracting the sand-tube II within the tube I, when that tube takes a cylindrical form at its exitend, a converging. jet may be obtained to operate upon the protruded sand or cutting material; but the efficiency of this arrangement as compared with that just described is not such as to recommend its adoption.

Where in the claim I use the word sand it will be understood that I do not mean to refer only to small particles of silicious material, but to any mass of small hard particles such as are capable of being used in the sandblast, and by the word fluid I intend to refer to any fluid, whether in a liquid, gaseous, or vaporous formas, for instance, water, air, or steamall of which have been successfully used in the sandblast; and in referring to the passages which inclose the sand-passage I of course intend to include a construction in which a continuous passage incloses the sandtube, as well as a construction in which the inclosing-passage is broken by partitions or the sand-passage and inclined to it so as to arranged in two parallel lines. converge toward the sand-jet and to a point Having now described my invention, I dein front of and clear of the mouth-piece. clal'e that What I claim is J. E. MATHEWSON. 5 In a sand-blast apparatus, the combination Witnesses:

of a sand-passage with passages for the im- H. K. WHITE,

pelling-fiuid arranged to substantially inolose G. H. G. MATHIESON. 

